The present invention relates generally to an image display system for displaying image information from measuring equipment, such as an echo sounder, and more particularly, the invention is concerned with a display system which can display more than one kind of image information received from a plurality of measuring devices in an integrated manner.
Today""s modern fishing vessels and pleasure craft are equipped with a radar 1, a course plotter 2 incorporating, or connected to, a Global Positioning System (GPS) receiver, an echo sounder 3, and so on, as shown in FIG. 1. In a conventional onboard system of this kind, a dedicated indicator M1 is connected to the radar 1 by three signal lines for red (R), green (G) and blue (B) signals, signal lines for horizontal (H) and vertical (V) synchronizing signals. Similarly, an indicator M2 is connected to the course plotter 2 by its R, G and B signal lines and two synchronizing signal lines, while an indicator M3 is connected to the echo sounder 3 by its R, G and B signal lines and two synchronizing signal lines.
Since the aforementioned indicators M1-M3 are usually provided in a ship""s bridge, the same number of additional indicators and signal lines become necessary if it is desired to monitor the same pictures as shown on the indicators M1-M3 in a remote location, such as a cabin, for example. The conventional onboard system has therefore been associated with the following problems:
A number of expensive indicators are required.
It is difficult to provide space for installing such multiple indicators.
Since three different pictures are individually shown on separate display screens, it is difficult for a viewer to give his or her consistent attention to the individual pictures, and this would result in a likelihood that the viewer could overlook important information.
This invention is intended to solve the aforementioned problems of prior art technology. Accordingly, it is an object of the invention to provide a display system which makes it possible to selectively present one or more images on an indicator by choosing them from multiple image signals or to set a desired measuring range and other operational parameters by making such choice or settings on the relevant indicator.
In one aspect of the invention, a display system can present a single image or multiple images on an indicator using image signals fed from a plurality of measuring devices.
To present multiple images on the single indicator, it is essential that image signals from the individual measuring devices be delivered with precisely controlled timing. For this purpose, the display system comprises a synchronizer for synchronizing horizontal and vertical synchronizing signals of the individual measuring devices with one another.
The display system also comprises an image selector for selectively switching to desired image signals during each successive horizontal scanning period or vertical scanning period to make it possible to present two different images, which are arranged horizontally or vertically, for instance, on the indicator screen.
Horizontally or vertically arranged multiple images can be displayed on the indicator by using the image signals, whichever selected by the image selector, based on the horizontal and vertical synchronizing signals.
The images to be displayed can be selected from the indicator if there is provided means for transmitting an image selection command from the indicator to the image selector.
When two image signals A, B are selected for the same display area of the indicator screen, two different images are superimposed in that display area. If, however, one of the image signals (image signal A, for example) has a dominantly high signal level, the other image signal B would be completely buried. To prevent this from happening, the display system in one varied form further comprises an image priority allocator which gives first priority to one of the two image signals in selecting a foreground image in image overlay mode. The display system of this variation makes it possible to clearly present a desired image in the foreground.
In another varied form of the display system, control signals for setting measuring ranges and other operational parameters of the multiple measuring devices are transmitted from the indicator to the measuring devices through a control line. This makes it possible to remotely control the individual measuring devices from the indicator.
In still another varied form of the display system, a plurality of indicators are parallel-connected and image selection commands and measuring range setting commands can be transmitted from any of the indicators through a common control line. The display system of this variation makes it possible to select desired images and set measuring ranges and other operational parameters of the individual measuring devices from any indicator.
In another aspect of the invention, a display system can present images on a plurality of indicators in different display modes using image signals fed from a plurality of measuring devices.
To make it possible to present different images on the multiple indicators, the display system comprises dedicated image selectors provided to the individual indicators. If the image signals are supplied directly from the multiple measuring devices to the individual indicators, more than one signal line would be required. To avoid this inconvenience, the display system of the invention comprises an RGB signal mixer which combines R, G and B image signals output from each of the measuring devices into a single video signal, and each of the image selectors includes means for separating the combined video signal of each measuring device into its original R, G and B image signals.
These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings.